Scheme for reducing audible noise developed by an extra-high voltage transmission line

ABSTRACT

A scheme for reducing the audible noise developed by an extrahigh voltage transmission line during a rainstorm. The scheme involves a plurality of disklike members of electrical insulating material mounted on the line conductor at spaced locations sufficiently close together that most of the rain water dropping off the conductor during a heavy rainstorm does so via dropreleasing regions on the disklike members which are spaced a substantial distance from the conductor.

United States Patent [15] 3,641,251 Liao 1451 Feb. 8, 1972 [54] SCHEME FOR REDUCING AUDIBLE 3,286,019 11/1966 McLoughlin et a1 ..174/l27 X NOISE DEVELOPED BY AN EXTRA- I-IIGH VOLTAGE TRANSMISSION LINE [72] lnventor: Tseng W. Ijao, Media, Pa.

[73] Assignee: General Electric Company [22] Filed: Oct. 16, 1970 [21] Appl. No.: 81,362

[52] US. CL ..l74/40 R, 174/42, 174/127 [51] Int. Cl. ..II02g 7/00 [58] Field ofSearch ..174/40 R, 40 TD, 42, 43, 45 R, 174/45 TD, 70 R, 70 A,111,127,135, 211

[56] References Cited UNITED STATES PATENTS 426,198 4/1890 Munsie ..174/45 R 1,171,936 2/1916 Faccioli 174/127 1,676,006 7/ 1928 Crook ..174/42 2,858,359 10/1958 Pearson ....l74/2ll X 3,246,073 4/1966 Bouche et al. ..l74/42 3,286,020 ll/l966 McLoughlin FOREIGN PATENTS 0R APPLICATIONS 639,040 6/1950 Great Britain ..174/127 734,092 7/1955 Great Britain..... ..174/40 r1) 1,131,353 10/1968 Great Britain ..174/42 Primary Examiner--Laramie E. Askin Attorney-J. Wesley Haubner, William Freedman, Frank L. Neuhauser, Oscar B. Waddell and Joseph B. Forman [5 7] ABSTRACT A scheme for reducing the audible noise developed by an extra-high voltage transmission line during a rainstorm. The scheme involves a plurality of disklike members of electrical insulating material mounted on the line conductor at spaced locations sufficiently close together that most of the rain water dropping off the conductor during a heavy rainstorm does so via drop-releasing regions on the disklike members which are spaced a substantial distance from the conductor.

4 Claims, 3 Drawing Figures SCHEME FOR REDUCING AUDIBLE NOISE DEVELOPED BY AN EXTRA-HIGH VOLTAGE TRANSMISSION LINE This invention relates to a scheme for reducing the audible noise developed by an extra high voltage (El-IV) transmission line during a rainstorm and, more particularly, relates to an audible-noise reducing scheme that controls the manner in which rain accumulating on the conductor is allowed to drop from the conductor.

In referring hereinafter to an extra high voltage (El-IV) transmission line, I am referring to those transmission lines rated for voltages of between about 345 kv. and 765 kv.

It is known that the audible noise developed by an extra high voltage transmission line during foul weather, particularly rain, is much greater than during fair weather. It appears that this audible noise is associated with water dropping from the conductor after it has accumulated thereon.

One way of reducing the audible noise level is to reduce the voltage gradient at the surface where the drops are being released into the surrounding air. This can be done by increasing the diameter of the conductor for a given line voltage or by covering the conductor with heavy electrical insulation. Both of these approaches are expensive, however, and the latter approach has the additional disadvantage of increasing the conductor temperature under load conditions since the electrical insulation acts also as thermal insulation.

An object of my invention is to provide inexpensive means for reducing the audible noise developed by an extra high voltage transmission line during a rainstorm without increasing the conductor diameter and without significantly raising the conductor temperature.

My invention is applied to a conventional extra high voltage transmission line that comprises an elongated metal conductor and a pair of insulating supports for supporting said conductor at widely spaced support points. The conductor sags as it extends between the support points and is bare throughout most of its length between the support points. In carrying out my invention in one form, I mount on the conductor at spaced locations between said support points a plurality of disklike members of electrical insulating material. Each of these members has an external surface that extends between said conductor and a drop-releasing region beneath said conductor spaced a substantial distance from said conductor. Each of the disklike members has a bore that surrounds the conductor so closely that rain water running along the conductor into the region of said member is intercepted by said member and caused to run along the external surface of the member to said drop-releasing region. The disklike members are spaced sufficiently close together along the conductor that most of the rain water dropping off said length of conductor during a heavy rainstorm does so via said drop-releasing region on said disklike members.

For a better understanding of the invention, reference may be had to the following description taken in conjunction with the accompanying drawings, wherein:

FIG. 1 is a schematic showing of a high-voltage transmission line embodying one form of my invention.

FIG. 2 is an enlarged sectional view taken along the line 2- 2 of FIG. 1.

H6. 3 is a sectional view taken along the line 33 of FIG. 2.

Referring now to FIG. I, there is schematically shown an extra high voltage transmission line comprising an elongated conductor and two conductor-supporting towers 12 located at widely spaced locations for supporting the conductor in midair high above the earth 13. Each tower includes a cross beam 14, from which is suspended a porcelain insulating support 16. The conductor 10 is supported on the porcelain insulating supports 16 at their lower ends. Since these parts may all be of conventional design, they are shown in schematic form only in FIG. I.

As pointed out hereinabove, the main problem that the present invention is concerned with is reducing the audible noise developed by such a transmission line. Such audible will reach its highest level during foul weather conditions, especially rain. It appears that this audible noise is associated with water dropping from the conductor after an accumulation has built up thereon.

In studying this problem, I have observed that the water accumulating on the conductor as rain falls thereon does not immediately drop from the conductor but runs along the conductor length. Because the conductor sags considerably in the region between supports, gravity causes the accumulated water to run toward the center of the span. in a stranded conductor, such as depicted in FIGS. 2 and 3, drops of water run along the conductor length between the strands, increasing in size as they move. When the drop reaches some critical size, dependent upon the rate of rainfall, the amount of sag and the diameter of the strands, it falls from the conductor.

For controlling the manner in which water falls from the conductor, I provide the conductor with a plurality of disklike members 20 of electrical insulating material. Each of these disklike members 20 is preferably of the design shown in detail in the sectional views of FIGS. 2 and 3.

Referring to FIG. 2, it will be noted that the member 20 has a bore 21 that closely surrounds the high-voltage conductor 10. The illustrated conductor 10 is of the type commonly referred to as ACSR. It comprises a plurality of aluminum strands 22 on its outer periphery helically wound about a stranded steel core 24. The insulating material of member 20 immediately surrounding the bore is relatively soft and resilient and is capable of deforming to generally conform to the slightly irregular outer periphery of the stranded conductor 10. The close fit that is present between the bore of the disk member 20 and the outer periphery of conductor 10 prevents any appreciable amount of the water running along the length of the conductor from finding a path through the bore of disk member 20. Such water is intercepted by the disk member 20 at one axial end of the bore 21 and is caused to run along the external surface 27 of the disk member to a dropreleasing region 30 at the lower end thereof, where it drops into the surrounding air.

It appears that the audible noise level of a high-voltage conductor from which water is dropping varies directly with the voltage gradient at the surface location where the drops are being released into the surrounding air. The highest voltage gradient is located immediately adjacent the external surface of the conductor 10, and any drops that fall directly from this surface into the surrounding air will produce the greatest amount of audible noise. My drop-releasing zone 30, being radially spaced from the conductor 10 by a relatively large amount of insulation, is located in a region of relatively lowvoltage gradient. Hence, drops released from zone 30 will produce relatively little audible noise.

By using the disk members 20 (a) to intercept most of the water that runs along the conductor 10 and (b) to force this water to drop from the line into the surrounding atmosphere at zones 30, I am able to force most of the accumulated water to drop from the line at regions of low-voltage gradient. Very little water falls from the line at the surface of the conductor where the voltage gradient is high. Hence, I am able to appreciably reduce the audible noise level of the line as compared to that present with a bare conductor 10 having no members comparable to 20 thereon.

The distance that a water drop, during a rainstorm, can run along the lengthrof a bare conductor, such as 10, before reaching a critical size that causes it to fall off the conductor depends upon the sag of the conductor, upon the diameter of its strands, and upon the rate of the rainfall. In a preferred form of my invention, I locate the disk members 20 sufficiently close together along the conductor length to intercept substantially all water running along the conductor before it can drop directly from conductor, even during the worst conditions normally expected, i.e., the heaviest anticipated rainfall and when sag is at a minimum value expected to occur during a heavy rainfall.

A significant advantage of my noise-reducing arrangement is that conductor 10 can remain bare over almost all of its length between the insulating supports 16. l have considered applying a thick insulating coating over this entire length of conductor for noise reducing purposes, but such an insulating coating is quite expensive and, moreover, constitutes a thermal barrier which causes the conductor to operate at a higher temperature for a given diameter and current than a bare conductor. Since my members 20 cover only a tiny percentage of the conductor length and the remainder remains bare, the members 20 have virtually no effect on conductor temperature.

To facilitate assembling each disk member 20 about its conductor 10, I provide the disk member with a slit 31 that extends generally radially from its bore to its outer periphery in its upper half. The disk member is sufficiently flexible to allow the slit 31 to be opened a sufficient distance to permit the conductor 10 to be slipped therethrough.

The bore 21 of each disk member is preferably coated with a thin layer of conductive or semiconductive material in order to minimize the chance for corona formation across any air space between the conductor and the bore 21.

To assist each disk member in maintaining its position on the conductor, I prefer to make the disk member relatively thick, considered axially of its bore 21, in the region adjacent this bore. This provides for more surface contact between the conductor 10 and the resilient disk member, thus reducing the chance for relative movement.

By making the portion of the disk member that extends downwardly from conductor 10 relatively long, I can locate drop-releasing zone 30 a relatively great distance from the conductor. Since the remainder of the periphery of the disk member is not used for drop releasing purposes, it can be located relatively close to the conductor, thereby reducing the amount of material needed for each disk member and reducing the wind loads likely to be developed on the disk member.

The disk member 20 can be made of any suitable plastic material which is resilient, electrically insulating, and durable in the environment of the transmission line. Examples of such materials are polycarbonate resin, sold by General Electric Co. under the trademark Lexan; polyolefin resin, sold by General Electric Co. under the trademark Vulkene; polyethylene; and ethylene-propylene elastomer.

By way of example and not limitation, a typical diameter of the EHV conductor 10 is between about 1 and 1% inches, and the dimension of the disk-member 20 as measured from the center line of the conductor to the drop-releasing region 30 is typically about three times the conductor diameter.

While I have shown and described a particular embodiment of my invention, it will be obvious to those skilled in the art that various changes and modifications may be made without departing from my invention in its broader aspects; and I,

therefore, intend herein to cover all such changes and modifications as fall within the true spirit and scope of my invention.

What I claim as new and desire to secure by Letters Patent of the United States is:

1. In an extra high voltage transmission line that is exposed to rainfall comprising an elongated metal conductor and a pair of insulating supports supporting said conductor at widely spaced support points, said conductor sagging between said support points and having an external surface that is bare throughout most of its length between said support points; means for reducing the audible noise developed by said line during rainfall comprising:

a. a plurality of disklike members of electrical insulating material mounted on said conductorat spaced locations between said support points,

b. each of said members having an external surface that extends between said conductor and a drop-releasing region beneath said conductor spaced a substantial distance from said conductor,

c. each of said disklike members having a bore that surrounds said conductors so closely that rain water running along said conductor into the region of said disklike member is intercepted by said member and caused to run along the external surface of said member to said dropreleasing region,

d. said disklike members being spaced sufficiently close together along said conductor that most of the rain water dropping off said length of conductor during a heavy rainstorm does so via said drop-releasing regions on said disklike members.

2. The noise-reducing arrangement of claim 1 in which each of at least some of said disklike members comprises an outer peripheral surface surrounding said conductor, the lowermost zone of said outer peripheral surface constituting said dropreleasing region, said outer peripheral surface being spaced a greater distance from said conductor in its lowermost zone than elsewhere.

3. The noise reducing arrangement of claim 1 in which each of at least some of said disklike members:

a. is at least partially of a resilient plastic material that tightly grips said conductor and b. has a slit therein extending from said bore to the outer periphery of said member, said slit being openable sufficiently during assembly of said member on to said conductor to allow said conductor to pass through said slit and into said bore.

4. The noise reducing arrangement of claim 1 in which each of at least some of said disklike members has a substantially greater thickness, considered axially of said conductor, in the region immediately surrounding said conductor than in regions disposed radially outwardly thereof. 

1. In an extra high voltage transmission line that is exposed to rainfall comprising an elongated metal conductor and a pair of insulating supports supporting said conductor at widely spaced support points, said conductor sagging between said support points and having an external surface that is bare throughout most of its length between said support points; means for reducing the audible noise developed by said line during rainfall comprising: a. a plurality of disklike members of electrical insulating material mounted on said conductor at spaced locations between said support points, b. each of said members having an external surface that extends between said conductor and a drop-releasing region beneath said conductor spaced a substantial distance from said conductor, c. each of said disklike members having a bore that surrounds said conductors so closely that rain water running along said conductor into the region of said disklike member is intercepted by said member and caused to run along the external surface of said member to said drop-releasing region, d. said disklike members being spaced sufficiently close together along said conductor that most of the rain water dropping off said length of conductor during a heavy rainstorm does so via said drop-releasing regions on said disklike members.
 2. The noise-reducing arrangement of claim 1 in which each of at least some of said disklike members comprises an outer peripheral surface surrounding said conductor, the lowermost zone of said outer peripheral surface constituting said drop-releasing region, said outer peripheral surface being spaced a greater distance from said conductor in its lowermost zone than elsewhere.
 3. The noise reducing arrangement of claim 1 in which each of at least some of said disklike members: a. is at least partially of a resilient plastic material that tightly grips said conductor and b. has a slit therein extending from said bore to the outer periphery of said member, said slit being openable sufficiently during assembly of said member on to said conductor to allow said conductor to pass through said slit and into said bore.
 4. The noise reducing arrangement of claim 1 in which each of at least some of said disklike members has a substantially greater thickness, considered axially of said conductor, in the region immediately surrounding said conductor than in regions disposed radially outwardly thereof. 